The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Piezoelectric devices are often used in small, compact, light-weight motor and energy harvesting applications. Piezoelectric motors provide mechanical energy that can be used to generate mechanical work while piezoelectric energy harvesters utilize vibrations from the surrounding environment to produce electrical energy. In motor applications, a voltage is applied to a structure, e.g., a beam, comprising a piezoelectric material that causes the piezoelectric structure to flex or bow. The voltage is applied across one of the piezoelectric layers causing this first layer to elongate, while substantially simultaneously, a reverse voltage is applied across the other piezoelectric layer causing the second layer to shorten. Thus, the beam is caused to bow, or flex, resulting in a physical displacement of at least a portion of the beam. This displacement can be utilized to provide mechanical work. For example, the polarity of the applied voltages can be cyclically alternated such that the portion of the piezoelectric beam that is displaced oscillates between displacement in a first direction and displacement in an opposite second direction. This oscillating displacement can be utilized to provide mechanical energy, or work. For example, the oscillating displacement can be used to drive a piston of a pneumatic device.
In energy harvesting applications, commonly referred to as vibration energy harvesting (VEH), relative motion is developed, and hence energy, between a vibrating structure and a piezoelectric structure, e.g., a piezoelectric beam. Due to the physical characteristics of the piezoelectric beam, this mechanical energy can be converted into electrical energy by developing cyclic stress in the beam. The vibration of the piezoelectric beam results in electrical charge accumulation in a piezo material used in fabrication of the beam. The charge accumulation results in an increase in voltage potential between two points of the piezoelectric beam, e.g., between opposing sides of the beam. This voltage potential can be harvested and used to provide power to various electrical load devices.
In various applications, the piezoelectric beam is constructed of a piezoelectric body having a roller pin at each of opposing distal ends. The body is typically fabricated of a flexible substrate, e.g., a carbon fiber substrate, sandwiched between two layers of piezoelectric material, e.g., two layers of piezoelectric ceramic material. The roller pins are typically affixed to the body distal ends using discrete roller pin tabs. The roller pin tabs are generally a machined composite, e.g., a fiberglass composite, having a flat surface that is affixed to distal ends of the body and reservoir or channel in which the roller pin is affixed, e.g., affixed using an epoxy. Additionally, in many instances, particularly in VEH applications, the piezoelectric beam includes a mounting tab around a center portion of the body that is used to connect the piezoelectric beam to the vibration structure from which energy is to be harvested. Alternatively, in motor applications, the mounting tab can be used to connect a mechanical device to which the beam is to deliver work, e.g., a piston. Typically, the mounting tab is clamped around the body and then glued, e.g., using an epoxy, to the body.
Typically, the body, the rollers, the roller pin tabs and the mounting tab are independently fabricated and then hand assembled to construct the complete piezoelectric beam. Independently fabricating and hand assembling the components requires considerable fabrication costs and assembly time. Accordingly, there exists a need for a less costly and time consuming method of manufacturing such piezoelectric beams.